Patino Manuel, Prochowski Andrea, Agrawal Mukta D, Simeone Frank J, Gupta Rajiv, Hahn Peter F, Sahani Dushyant V
From the Division of Abdominal Imaging, Department of Radiology (M.P., A.P., M.D.A., F.J.S., R.G., D.V.S.), and Department of Abdominal Imaging and Intervention (P.F.H.), Massachusetts General Hospital and Harvard Medical School, 55 Fruit St, Boston, MA 02114.
Radiographics. 2016 Jul-Aug;36(4):1087-105. doi: 10.1148/rg.2016150220.
Dual-energy (DE) computed tomography (CT) offers the opportunity to generate material-specific images on the basis of the atomic number Z and the unique mass attenuation coefficient of a particular material at different x-ray energies. Material-specific images provide qualitative and quantitative information about tissue composition and contrast media distribution. The most significant contribution of DE CT-based material characterization comes from the capability to assess iodine distribution through the creation of an image that exclusively shows iodine. These iodine-specific images increase tissue contrast and amplify subtle differences in attenuation between normal and abnormal tissues, improving lesion detection and characterization in the abdomen. In addition, DE CT enables computational removal of iodine influence from a CT image, generating virtual noncontrast images. Several additional materials, including calcium, fat, and uric acid, can be separated, permitting imaging assessment of metabolic imbalances, elemental deficiencies, and abnormal deposition of materials within tissues. The ability to obtain material-specific images from a single, contrast-enhanced CT acquisition can complement the anatomic knowledge with functional information, and may be used to reduce the radiation dose by decreasing the number of phases in a multiphasic CT examination. DE CT also enables generation of energy-specific and virtual monochromatic images. Clinical applications of DE CT leverage both material-specific images and virtual monochromatic images to expand the current role of CT and overcome several limitations of single-energy CT. (©)RSNA, 2016.
双能量（DE）计算机断层扫描（CT）提供了基于原子序数Z以及特定材料在不同X射线能量下独特的质量衰减系数来生成特定材料图像的机会。特定材料图像提供了有关组织成分和造影剂分布的定性和定量信息。基于DE CT的材料表征的最重要贡献来自于通过创建专门显示碘的图像来评估碘分布的能力。这些碘特异性图像增加了组织对比度，并放大了正常组织与异常组织之间衰减的细微差异，改善了腹部病变的检测和特征描述。此外，DE CT能够从CT图像中通过计算去除碘的影响，生成虚拟平扫图像。还可以分离包括钙、脂肪和尿酸在内的几种其他物质，从而对代谢失衡、元素缺乏以及组织内物质的异常沉积进行成像评估。从单次增强CT采集中获取特定材料图像的能力可以用功能信息补充解剖学知识，并且可用于通过减少多期CT检查中的期数来降低辐射剂量。DE CT还能够生成能量特异性和虚拟单色图像。DE CT的临床应用利用特定材料图像和虚拟单色图像来扩展CT当前的作用，并克服单能量CT的一些局限性。（©）RSNA，2016年。
